A switch fabric (SF) may include one or more stages of switch elements, as shown in FIG. 1, FIG. 2, FIG. 3, and FIG. 4. The SF shown in FIG. 1 and FIG. 2 includes a stage-0 switch element (S0) and multiple line cards (LCs). The SF shown in FIG. 3 and FIG. 4 includes three stages of switch elements and multiple LCs. In FIG. 1 and FIG. 3, the LC that sends uplink data flows (ingress LC) is located on one side of the switch element, and the LC that receives downlink data flows (egress LC) is located on the other side of the switch element. The LC in FIG. 2 and FIG. 4 can send uplink data flows and can also receive downlink data flows. In FIG. 4, the S1/3 includes two parts: a stage-1 switch element (S1), and a stage-3 switch element (S3). The packets sent by a source LC carry the information about a destination LC. The packets pass through the S1, stage-2 switch element (S2), and S3, and arrive at the destination LC. The packets include variable-length packets and fixed-length cells.
In a common multi-stage SF, both the LC and the S1/3 are generally located in a line card chassis (LCC). The S1/3 includes two parts: the S1, and the S3, where the S1 corresponds to the S3. In this case, the S1 and S3 may be located on the same physical component or on different physical components. The S1 may be connected to the S3 through a specific interface; the S2 is generally located in a fabric card chassis (FCC), and the FCC is connected to the LCC through optical fibers or cables, as shown in FIG. 5. According to a specific algorithm such as a load balancing algorithm, the S1 in the LCC selects an S2, and forwards the packets sent by the source LC to the FCC through optical fibers, and a repeater (RPT) in the FCC forwards the packets to the S2. The S2 switches the packets to the S3 in the LCC according to the destination LCC information carried in the packets. Finally, the S3 in the destination LCC switches the packets to the destination LC according to the destination LC information carried in the packets. The FCC may have no RPT.
The defects of the prior art are:
In practice, users may achieve system expansion by connecting multiple LCCs in a single-stage SF to an FCC. In this case, the switch elements that are configured as S0s in the LCC need to be changed to S1/3.
As described above, after system expansion is achieved, packets in all LCCs must pass through the S2 in the FCC before being switched, even if the source LC and the destination LC are located in the same LCC. That is to say, after system expansion, the LCC loses the function of local switching. Thus, sufficient interconnection bandwidth is required between the LCC and the FCC in order to meet the performance requirement and the system costs are increased. In addition, the switching performance of the system may be degraded because the traffic flowing to the S2 increases.